Polymers that display increased solubility in a developer after undergoing main chain scission through irradiation with ionizing radiation, such as an electron beam, or short-wavelength light, such as ultraviolet light, are conventionally used as main chain scission-type positive resists in fields such as semiconductor production. (Hereinafter, the term “ionizing radiation or the like” is used to refer collectively to ionizing radiation and short-wavelength light.)
PTL 1 discloses one example of a main chain scission-type positive resist having high sensitivity. The disclosed positive resist is formed from an α-methylstyrene-methyl α-chloroacrylate copolymer including an α-methylstyrene unit and a methyl α-chloroacrylate unit.